Code p0170 refers to fuel trim(FT) bank 1 malfunction====causes --intake leak--AIR system--fuel pressure/pump---injectors---EVAP canister purge valve---HO2S
it also refers to heated oxygen sensor(HO2S) 3 bank1 circuit malfunction===causes --wiring---HO2S--- ECM
there is a long explanation for fuel trim but basically it is this
when the ECM and the car is new, there are parameters set that the ECM continually moniters and sets as a base line for performance
If it continually reads different but constant parameters, the ECM will reset itself to adopt the new parameters as the base line
When there is a problem that continually affects this base line ( vacuum leaks , oxygen sensor faults, wiring , low fuel pressure faulty injectors etc , the ECM cannot trim the air/fuel ratio for max performance so it throws up an error code (P0170) which is asking for assistance so that it can do the job it was programmed to do
You may have noticed this fuel trimming if you do a lot of city driving then go for a long trip at a constant speed where after a while driving you feel that it requires less accelerator to maintain the same road speed ( better economy for highway driving)
That is the new base line for the trim
it alters back after you go back to city driving
Many things can cause this. O2 sensor, vacuum leaks, wiring,and more. It needs to go on a scanner to isolate the problem. It could be $3.00 worth of vacuum hose or several hundred dollars for gasket replacement.
The code P0170 means that the air-fuel mixture coming in to the engine is too lean, or too rich. Usually it's the lean condition that causes this code. The code P0173 means the same, only for the Bank 2. Some car manufacturers list the description for the code P0170 as self adaptation out of limits.
The code P0170 could be caused by a number of reasons, such as vacuum leaks, bad PCV valve, or other parts of crankcase ventilation system, low fuel pressure, bad oxygen sensor, bad MAF sensor or even a bad EGR vlave.
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